clang vs llvm-gcc-4.2 with py27-matplotlib

[Adam Mercer]

Hi

In #31046 [1] py27-matplotlib is failing to build with Xcode-4.2, the
compiler being used is clang. When I try to reproduce this on my Lion
system with Xcode-4.2 I can't, my system builds the port using
llvm-gcc-4.2. Does anyone have any idea why one system would use clang
and another llvm-gcc-4.2? Is there some configuration option that
would control this?

Cheers

Adam

[1] <https://trac.macports.org/ticket/31046>